Neurabin-II/spinophilin. An actin filament-binding protein with one pdz domain localized at cadherin-based cell-cell adhesion sites.
In a preceding paper, we reported a novel actin filament (F-actin)-binding protein, named neurabin, which was specifically expressed in neural tissue and implicated in neurite formation. We purified from rat brain another F-actin-binding protein, which had a domain organization similar to that of neurabin but was ubiquitously expressed, and named it neurabin-II. The original neurabin, renamed neurabin-I, had 1095 amino acids and a calculated Mr of 122,729, whereas neurabin-II had 817 amino acids and a calculated Mr of 89, 642. Both neurabin-I and -II had one F-actin-binding domain at the N-terminal region, one PDZ domain at the middle region, a domain known to interact with transmembrane proteins, and domains predicted to form coiled-coil structures at the C-terminal region. Both neurabin-I and -II bound along the sides of F-actin and showed F-actin-cross-linking activity. The subcellular distribution analysis indicated that neurabin-II was enriched at the postsynaptic density fraction in rat brain and the adherens junction fraction in rat liver. Immunofluorescence microscopic analysis revealed that neurabin-II was highly concentrated at the synapse in primary cultured rat hippocampal neurons and at the cadherin-based cell-cell adhesion sites in Madin-Darby canine kidney cells. Neurabin-II turned out to be the same as a recently reported protein phosphatase 1-binding protein named spinophilin. These results suggest that neurabin-II/spinophilin plays an important role in linking the actin cytoskeleton to the plasma membrane.
Satoh
A
A
Takai Biotimer Project, ERATO, Japan Science and Technology Corporation, JCR Pharmaceuticals Co., Ltd., Kobe 651-22, Japan.
Nakanishi
H
H
Obaishi
H
H
Wada
M
M
Takahashi
K
K
Satoh
K
K
Hirao
K
K
Nishioka
H
H
Hata
Y
Y
Mizoguchi
A
A
Takai
Y
Y
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins; D002448:Cell Adhesion; D002460:Cell Line; D004285:Dogs; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009479:Neuropeptides; D011817:Rabbits; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions; D000099273:Neurabins
D000199:Actins; D015820:Cadherins; D002352:Carrier Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D000099273:Neurabins